<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <input type="button" value="禁用文本框" id="bn">
    <input type="text"  value="" id="tt">
    <script>
     function my$(id){
         return document.getElementById(id);
     }

    my$("bn").onclick = function (){
        my$("tt").disabled = true;
    }

    </script>
</body>
</html>